1. Field of the Invention
The invention is based on a gas-blast breaker according to the first part of claim 1.
2. Discussion of Background
The invention relates to a prior art of gas-blast breakers as is described, for example, in DE-A1-3321 740. The known breaker exhibits two contact members arranged in an insulating gas-filled housing and an insulating material nozzle of several segments arranged successively in the circumferential direction. The segments are loaded via springs with a force acting centripetally. As a result, one of the two contact members can be guided through the insulating material nozzle in the closed position of the breaker and, when opening, the diameter of the constriction of the insulating material nozzle is considerably reduced compared with the diameter determined by the contact member guided through in the closed position. Such a breaker is characterized by good related-current carrying capacity with good quenching capability and without using additional rated-current contacts. However, when large short-circuit currents are interrupted, the insulating material nozzle is subjected to great erosion which considerably increases the diameter of the nozzle constriction and makes it considerably more difficult to build up sufficient quenching gas pressure. In addition, the contact member guided through the nozzle constriction collides undamped and at high speed with the segments of the insulating material nozzle in an O-C-O switching cycle and causes unwanted mechanical stresses during this process.